The present invention relates to growth of single crystals of phosphorus compounds, and, in particular, relates to the growth of single crystals of indium phosphide, and, in greater particularity, relates to the process and apparatus of preparing the materials and the in-situ growth of the crystals from the materials.
Bulk indium phosphide crystals are commercially grown by a two-step process: synthesis of the polycrystalline compound in one furnace followed by growth of the single crystal in another. Transferring the material from one furnace to another requires time and care to avoid the possibility of contamination. Furthermore, since stoichiometry is controlled only during the first step, it is difficult to prevent phosphorus loss in step two when heating/remelting the charge material. Prior art attempts at in-situ growth resulted in poor quality single crystals of unknown stoichiometry because it was very difficult to control the phosphorus vapor pressure during synthesis.
Several attempts to grow high quality single crystals having phosphorus of bulk dimensions have been made but none have successfully produced the quality of crystals made by the present invention. As shown in the prior art, an injector with phosphorus therein was suspended above the melt without any means for adjusting the height of the injector above the melt during the injection process. As a result it is impossible to control the stoichiometry of the melt and only results in an indium-rich melt. The quality of crystals grown from indium-rich melts is poor to say the least. The crystals have inclusions and precipitates, for example. A stoichiometric melt contains exactly 0.500 mole fractions of phosphorus. Further the crystals produced are twinned ones and twinned ones have no commercial value.